The invention relates to a filler wire, which is formed in random length from a tubular, metal jacket or covering and a pulverulent material filling surrounded by said jacket or covering, as well as to a process for the production thereof.
Filler wires, which are produced with random length, particularly for use in mechanized welding installations, have a tubular, metal covering, in whose interior is introduced a pulverulent material filling. Various processes and installations are known for the production of such filler wires.
In a known process (EP-A-3,370), a metal strip is shaped to form a channel, in which is introduced pulverulent filling material, after which the channel is shaped and welded in a welding station. For example, the introduced pulverulent filling material can be a mixture formed from different components, which e.g. have a flux-forming material, a slag-forming material and/or a material containing metals or metal oxides. Such mixtures suffer from the disadvantage that they separate during storage and then are introduced into the channel with a composition differing from the original composition of the mixture. The aforementioned risk of separation can admittedly be counteracted through the use of a pulverulent filling of agglomerated material particles, but this leads to increased production expenditure.
In order to ensure the flowability of the filling material, the particle size thereof must be kept correspondingly small. Thus, there is a risk of such particles being deposited on the longitudinal edges of the channel, which is open at the top, so that the welding process can be impaired and a clean weld is not formed. This disadvantage can in particular occur in the case of powder fillings having ferritic or ferromagnetic components, whose particles can be moved by the magnetic fields which appear during welding. It is admittedly known that this problem can be counteracted in that the introduced filling material is initially covered by a cover strip and only then is the channel compressed to form a tube and the longitudinal edges welded together, (DE-Al-25 15 342). Another solution of this problem consists of shaping a step-like reinforcing seam or fin on a longitudinal edge of the continuous strip used for producing the filling wire and by employing a profiling mechanism. During the compression of the channel, said reinforcing seam assumes a position with respect to the tube in which it covers the slit between the two longitudinal edges on the inside and consequently prevents the deposition of particles on said lateral edges (DE-Al-30 27 547). Although the extra production costs are limited, the additional material required for forming the reinforcing seam has a disadvantageous influence.